Vascular grafts of synthetic fiber are now widely used, a variety of constructions in a variety of materials being available. A principal factor in the selection of a particular graft is the porosity of the fabric of which the graft is composed. This factor is significant because the porosity controls both the tendency to hemorrhage and the ingrowth of tissue into the wall of the graft.
The general procedure for implantation of a graft includes the step of preclotting, a step in which the graft is immersed in the blood of the patient and then allowed to stand for a period long enough for clotting to ensue. As a result, when the graft is implanted surgically hemorrhaging does not occur; yet, growth of tissue into the wall of the graft can proceed. This growth is extremely important since, eventually, the wall of the graft simulates the wall of the vessel which it replaces and, if all goes properly, provides a lumen which remains open and free of clots.
The degree of adhesion of tissue to the wall of the graft varies with the material used. Thus, V. J. Lombardi in U.S. Pat. No. 3,561,441 discloses the use of a non-sticking material having loops thereon for use in convering and treating wounds. The material which he proposes to use is a polyfluorinated polyolefin in filament, spun or plastic ribbon form. Lombardi discloses that, as the result of using a non-sticking material, the fabric can be removed from a wound periodically as a step in the changing of the dressing without tearing open the wound itself.
L. R. Sauvage in U.S. Pat. No. 3,878,565 has disclosed a tubular textile synthetic cardio-vascular prosthesis of polyester or other synthetic fibers, the prosthesis consisting of a body having a multiplicity of fiber loops extending outwardly from the surface thereof. Also, as shown in his FIG. 2A, the body is crimped into irregular, circumferential corrugations. Such corrugations are intended to provide protection against kinking or collapse of the tubing and narrowing of the lumen thereof as the result of bending or other factors. However, the degree of protection afforded by such irregular corrugations varies over the length of the tube and can be below the required level of protection as the result of the corrugations being so irregular in shape and size.
While the construction of Sauvage facilitates growth of tissue exterior to the body or trellis of the tubular graft, the absence of loops on the interior of the tubing may result in exposure of the synthetic filaments of which the tubing is composed. Furthermore, the Sauvage graft is circularly-knit so that the technique which provides the fabric loops on the Sauvage graft is not applicable to warp-knit tubing.
As is evident, it would be desirable that a graft tubing be provided which has uniform strength and rigidity along its entire length, which is suitable for bifurcation and which facilitates growth of tissue along the interior thereof as well as on the outer surface thereof.